rhythmically complex works for Disklavier (computer-driven acoustic piano);
and

piano and ensemble music whose rhythmic complexity tends to be
milder and within a single tempo framework.

Of particular importance in most of his music is the concept of
repeating loops, ostinatos, or isorhythms
of different lengths going out of phase with each other; the idea
leads to simultaneous layers of different, mutually prime tempo
relationships in his Disklavier and electronic works, and is used
in a less obvious structural way in his live-ensemble music. This
concept can be traced back to suggestions in the rhythmic chapter
of Henry Cowell's book New Musical
Resources, but is also related here to inspirations from
astrology, into which Gann was drawn by
the writings of composer/astrologer Dane
Rudhyar.

Another thread in his work is the influence, both rhythmic and
melodic, of Native American
music, particularly that of the Hopi,
Zuni, and other Southwest Pueblo tribes. These tribes have in common a
technique of shifting back and forth between or among two or more
tempos within a song, the shifts sometimes correlated to dance
movements. Starting in 1984 with his political piece The Black
Hills Belong to the Sioux, Gann adopted a method of switching
between different tempos (usually between quarter-notes, dotted
eighths, triplet quarters, and other values) as a more performable
alternative to the simultaneous layers at contrasting tempos that
he had sought earlier under Charles Ives's influence. Ironically,
other composers had arrived at a similar technique via other
routes, coalescing into a New York style of the 1980s and '90s
called Totalism.

A common Gann strategy is to set a rhythmic process in motion and
use harmony (mostly triadic or seventh-chord-based, whether
microtonal or conventional) to inflect the form and focus the
listener's attention. Gann's microtonal music proceeds according to
Harry Partch's technique of tonality flux, linking chords through tiny
(less than a half-step) increments of voice-leading. In 2000, Gann
studied jazz harmony with John Esposito, and began using
bebop harmony as a basis for his
non-microtonal music, even in contexts not reminiscent of
jazz.